The present invention relates generally to containers for microwave cooking. The prior art includes numerous examples of utensils for cooking foodstuffs in a microwave oven partially or entirely by either direct or indirect steam heating of the foodstuff. For example, prior U.S. Pat. No. 4,560,850 discloses a microwave cooking container incorporating a steam port which opens to the interior of the container such that steam evolved from moisture in the foodstuff to be cooked upon heating thereof by microwave exposure passes through the steam port in heat exchange relationship with exterior surfaces of the container to thereby indirectly heat portions of the contained foodstuff by heating corresponding portions of the container. U.S. Pat. No. 4,529,089 discloses a food container having a baffle which receives ice chips. During cooking the ice chips are converted to steam which is then directed to the cooking chamber of the container for steaming of a foodstuff contained therein.
U.S. Pat. No. 4,501,946 discloses a device for cooking foods with microwaves wherein a water and vapor or steam space overlies a food containment chamber and communicates therewith by means of tubes hereby microwave energy converts water in the water space to steam which then is directed to the cooking chamber. U.S. Pat. No. 4,439,656 discloses a cooking container which is placed in a holder to define a space therebetween which is filled with liquid. The liquid absorbs microwave energy and heat, and the thermal energy is then transmitted through the food container and to the food contained therein. U.S. Pat. No. 4,413,167 discloses a microwave egg cooker wherein water in a container is heated to boiling by exposure to microwave radiation and the resulting steam heats a tray containing eggs such that the eggs are cooked by conduction rather than by microwave radiation. U.S. Pat. No. 4,317,017 discloses a steamer for use in a microwave oven wherein a water reservoir in the bottom of the steamer container is exposed to microwave radiation for heating of the water to produce steam. The foodstuffs to be steam cooked thereby shielded from exposure to microwave radiation.
Other U.S. Patents which include reference to evolution of steam or vapor in a microwave cooking utensil include U.S. Pat. Nos. 4,306,133; 4,027,132; 3,985,991; 3,985,990; and 3,854,023. U.S. Pat. No. 3,985,990 in particular discloses a chamber which can be filed with absorbent material to accumulate liquid waste products such as renderings from a foostuff being cooked. This patent also discloses a mode of operation for cooking wherein food is selectively heated, and so dried, by exposure to microwave radiation, and the hot vaper evolved from the drying is trapped to create a hot steam, heat insulating blanket encompassing the food. U.S. Pat. No. 3,411,433 discloses a foil product which forms a cooking or baking dish and is comprised of an upper, perforated layer of metal foil, an intermediate layer of absorbent material, and a lower or bottom layer of imperforate metal foil. Another patent of general interest with regard to the prior art of microwave cooking as it relates to the present invention is U.S. Pat. No. 3,777,099.
In spite of extensive efforts directed toward improvement of microwave cooking systems, there remains a need in the art for cooking systems and utensils which will permit a greater degree of control over distribution of thermal energy with the foodstuffs that are thawed, reheated or cooked in a microwave oven. This can comprise accelerated thawing of frozen foods, heating of thawed or refrigerated foodstuffs, cooking of raw foodstuffs including simmering or boiling of liquid foodstuffs, boiling of foods in water, baking of various foods including most notably pastry based foodstuffs such as pies, roasting, as of meats and the like, and steaming for any of a wide variety of foods including meats, vegetables, and even such pastry based foodstuffs as dumplings.
For any of the above examples, as well as others, any of a variety of microwave cooking techniques might be envisioned as the most desirable for proper cooking of the foodstuff. In the most general terms, proper cooking procedure of any given foodstuff will entail the exercise of control over the mode, intensity, and duration of the thermal energy to which the foodstuff is exposed.